Messages in this thread | | | Date | Thu, 1 Jun 2023 09:50:50 -0700 | From | Kees Cook <> | Subject | Re: [PATCH] x86/purgatory: Do not use fortified string functions |
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On Thu, Jun 01, 2023 at 09:45:57AM -0700, Dave Hansen wrote: > On 5/30/23 17:33, Kees Cook wrote: > > With the addition of -fstrict-flex-arrays=3, struct sha256_state's > > trailing array is no longer ignored by CONFIG_FORTIFY_SOURCE: > > > > struct sha256_state { > > u32 state[SHA256_DIGEST_SIZE / 4]; > > u64 count; > > u8 buf[SHA256_BLOCK_SIZE]; > > }; > > > > This means that the memcpy() calls with "buf" as a destination in > > sha256.c's code will attempt to perform run-time bounds checking, which > > could lead to calling missing functions, specifically a potential > > WARN_ONCE, which isn't callable from purgatory. > > > > Reported-by: Thorsten Leemhuis <linux@leemhuis.info> > > Closes: https://lore.kernel.org/lkml/175578ec-9dec-7a9c-8d3a-43f24ff86b92@leemhuis.info/ > > Bisected-by: "Joan Bruguera Micó" <joanbrugueram@gmail.com> > > Fixes: df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3") > > Cc: Thomas Gleixner <tglx@linutronix.de> > > Cc: Ingo Molnar <mingo@redhat.com> > > Hi Folks, > > The -fstrict-flex-arrays=3 commit isn't upstream yet, right? That makes
Correct.
> it a _bit_ wonky for us to carry this on the x86 side since among other > things, the Fixes commit doesn't exist. I'd be fine if this goes up > along with the -fstrict-flex-arrays=3 code, so: > > Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
That would be perfect; thank you! I've added it to my tree.
-- Kees Cook
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